1. Field of the Invention
The present invention relates generally to padlocks, and, more particularly, relates to an improved type of construction for padlocks that has very few parts and is easily assembled, thus resulting in lower cost. The preliminary form of such a padlock was disclosed in Disclosure Document No. 255756, filed in the U.S. Patent and Trademark Office on Jun. 18, 1990.
2. Description of the Prior Art
Various types of padlock constructions are well-known in the art. These constructions often have many assembly steps thus adding to the cost. For example, a lock plug is not usually simply inserted into the casing and held in place. Rather, a further assembly step is required to somehow secure the lock plug, as by driving a securing pin through the casing. Such securing steps often generate further assembly steps, such as grinding of the exposed edges of the securing pin. Multiple assembly steps are not limited to the lock plug, however, as assembly of the padlock is usually a multi-step process of some complexity. As a result, such padlocks have higher costs than a padlock that could be assembled more easily.
Another factor adding to the costs of most padlocks is the need for heavy tooling of the component parts. When a solid casing is used, the shackle opening and lock plug openings have to be drilled out. If steel is used, such drilling must be done before hardening, and the drilled body thereafter heat-treated to add security. Further, steel must be plated to prevent corrosion. Casings made of laminates can require even more tooling, as the individual strips must be tooled before they are joined. As mentioned above, tooling can also be required as a post-assembly step as in smoothing the surface of the lock after insertion of a securing pin. Use of such tooling adds time and expense to the making and assembly of a padlock.
It is thus desirable to provide a padlock that is easily and inexpensively assembled, and that does not require a great deal of tooling in its manufacture or assembly.